| 摘要 |
PURPOSE:To suppress totally an error of each tuning element by detecting a reception in-band frequency characteristic in response to the electric field strength, and controlling a tuning voltage of each tuning circuit individually to obtain a suitable frequency characteristic. CONSTITUTION:When the same tuning voltage is fed to each tuning circuit at the reception of a desired signal, the desired signal entering from a high frequency signal input terminal 8 holes an AGC voltage and a frequency sweep signal oscillated at a desired signal frequency band and swept generated by a tuning control circuit 10 is fed to a signal switching circuit 11. Switching circuits 21, 22 are connected to terminals 13, 15 and the frequency sweep signal is fed to a signal switching circuit 1 from the terminal 13 to send it to a high frequency amplifier 3. A frequency sweep signal is extracted from a connection point with an inter-stage tuning circuit 4 and inputted to a mixer 5 via the switching circuit 22. The signal of a local oscillator 7 is inputted to the mixer 5 and a signal obtained from the output terminal is fed to a signal level detection circuit 12, and the obtained DC voltage is fed to the tuning control circuit 10.
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